Disc brake apparatus have conventionally been known in general, in which rotor surfaces on both sides of a disc rotor are held by a pair of brake pads, while the rotary torque received by the brake pads from the rotor surfaces of the disc rotor is caught by a torque member (mounting), so as to obtain a braking force.
In such a disc brake apparatus, the brake pads typically have a structure in which a backing metal is joined to a pad member coming into frictional contact with the rotor surface of the disc rotor, while the backing metal has a first torque transmission part set at an end part to become the turning-out side during normal rotations (the turning-in side during reverse rotations) of the disc rotor and a second torque transmission part set at an end part to become the turning-out side during reverse rotations (the turning-in side during normal rotations of the disc rotor) of the disc rotor. Correspondingly, the torque member is provided with first and second torque receiving parts which receive the rotary torque from the disc rotor by opposing the first and second torque transmission parts of the backing metal of the brake pad, respectively.
Here, in order for the brake pad to slide in parallel with the rotary axis of the disc rotor, a predetermined clearance is provided between the first and second torque receiving parts of the torque member and the first and second torque transmission parts of the brake pad. Therefore, the first torque transmission part of the brake pad may abut against the first torque receiving part of the torque member at the time of braking during normal rotations of the disc rotor, thereby generating clunking sounds; while the second torque transmission part of the brake pad may abut against the second torque receiving part of the torque member at the time of braking during reverse rotations of the disc rotor, thereby generating clunking sounds.
Hence, disc brake apparatus for vehicles equipped with means for restraining such clunking sounds from occurring have been proposed in Patent Document 1 (Japanese Patent Application Laid-Open No. 2002-250376), Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-336555), and the like. The disc brake apparatus described in Patent Document 1 is directed to one in which a first pad retainer (pad clip) made of a sheet metal is interposed between the first torque receiving part of the torque member and the first torque transmission part of the brake pad, while a similar second pad retainer is interposed between the second torque receiving part of the torque member and the second torque transmission part of the brake pad.
In the disc brake apparatus described in Patent Document 1, the second pad retainer to become the turning-in side of the disc rotor at the time of forward braking of the vehicle is provided with a first spring action part which always biases the second torque transmission part of the brake pad toward the turning-out side of the disc rotor (the first torque receiving part side of the torque member) at the time of forward braking, and a second spring action part which elastically receives the second torque transmission part of the brake pad at the time of back braking of the vehicle.
On the other hand, the disc brake apparatus for a vehicle described in Patent Document 2 is directed to one in which a pad shim having a vibration damping effect is additionally provided with a backing metal of the brake pad in order to restrain the brake pad from generating high-frequency vibrations at the time of braking, thereby suppressing the occurrence of so-called brake noise phenomenon.
In the disc brake apparatus described in Patent Document 2, the pad shim is integrally provided with a first anti-clunk part which is arranged between the first torque transmission part of the backing metal of the brake pad and the first torque receiving part of the torque member and generates a spring force, and a second anti-clunk part which is arranged between the second torque transmission part of the backing metal of the brake pad and the second torque receiving part of the torque member and generates a spring force.